1. Introduction: Soil properties are affected by environmental conditions. Exposing of soil under multiple freeze thaw cycles may damage soil structure due to generated forces by water freezing and changes in mechanical and deformation features. Silty soils are highly susceptible for frost damage under the F-T cycles so, it is important to investigate their thermal and mechanical behavior. Thermal changes in susceptible soil often lead to irreversible creep deformation. The freeze and thaw cycles change soil engineering properties and mechanical behaviors by varying soil structure (Othman., 1992). A lot of research has devoted to study the effect of freezethaw cycles on the geotechnical properties of various soils (Wang et al., 2007). But, less laboratory works have studied the effect of freeze-thaw cycles on long term deformation and consolidation parameter of silty soil. Therefore, the aim of this paper is to determine the magnitude and rate of volume changes of soil specimen under 10 repeated cycles freeze and thaw which subjected to different vertical stresses...

A common method for Controlling a group of parallel converters in decentralized Control strategy structure in an island microgrid, the use is the droop-down characteristics of frequency ω-P and voltage E-Q. However, the problem with using this method is that the reactive power is not properly distributed (in proportion to the capacity of the micronutrients) between the micronutrients, which may lead to overload in the converters. Microgrids may also suffer from dynamic stability problems such as power fluctuations, which can be increased by switching between active and reactive power Control. To avoid this problem, the X / R ratio of transmission lines is an important parameter that should be carefully considered in the design of micronutrient Controllers. By linearizing and simplifying conditions, the Control system conversion function model becomes a single input-single output system, which is efficient enough to show the relationship between Control parameters such as slope of droop characteristics and derivative sentences, virtual impedance, and voltage Controllers. Using this model, stability conditions for different parameters are analyzed. Also, to improve power distribution stability, common droop strategies are modified by adjusting the slope as well as adding nonlinear sentence sections. This approach reduces the coupling between active and reactive power Control and reduces the dependence of power distribution on grid parameters such as the X / R ratio. To evaluate the reliability of the proposed model, the simulation results in a sample island microgrid in MATLAB software are presented.

Over the past few years, many electrical vehicle manufacturers have focused on developing enhanced Controller efficiency for Four-Wheel Drive (FWD) systems. The Control of the speed and direction of the FWD is crucial for safe and efficient operation, particularly in challenging maneuvers. The FWD system movements in straight routes and during maneuvers, turning all four wheels right and left, have not been well covered. Therefore, a robust Control design that is capable of Controlling the FWD system at an optimal time of operation is highly required. In this research, a Finite Time Control ((FTC)) is designed, implemented, and simulated to improve the robustness and performance of the FWD system during challenging maneuvers. The proposed (FTC) Controls both the speed and direction of all wheels of FWD according to the route situations. The proposed (FTC) is compared with an FWD system that is Controlled by a traditional Proportional, Integral, and Derivative (PID) Controller during straight moving and maneuvers. The comparison is based on Controlling parameters such as settling time, maximum overshoot, and speed error values. The results showed that the proposed (FTC) has a much faster settling time, significantly less maximum overshoot, and much lower error values than the PID Controller. These factors are considered the main features of the contribution of any Controller system that aims for optimal and robustness and (FTC) proved to have them adequately.

One of the issues of reliable performance in the power grid is the existence of electromechanical oscillations between interconnected generators. The number of generators participating in each electromechanical oscillation mode and the frequency oscillation depends on the structure and function of the power grid. In this paper, to improve the transient nature of the network and damping electromechanical fluctuations, a decentralized robust adaptive Control method based on dynamic programming has been used to design a stabilizing power system and a complementary static var compensator (SVC) Controller. By applying a single line to ground fault in the network, the robustness of the designed Control systems is demonstrated. Also, the simulation results of the method used in this paper are compared with Controllers whose parameters are adjusted using the PSO algorithm. The simulation results show the superiority of the decentralized robust adaptive Control method based on dynamic programming for the stabilizing design of the power system and the complementary SVC Controller. The performance of the Control method is tested using the IEEE 16-machine, 68-bus, 5-area is verified with time domain simulation.

Non-cooperative intelligent Control agents (ICAs) with dedicated cost functions, can lead the system to poor performance and in some cases, closed-loop instability. A robust solution to this challenge is to place the ICAs at the feedback Nash equilibrium point (FNEP) of the differential game between them. This paper introduces the designation of a robust decentralized infinite horizon LQR Control system based on the FNEP for a linear time-invariant system. For this purpose, two Control strategies are defined. The first one is a centralized infinite horizon LQR (CIHLQR) problem (i.e. a supervisory problem), and the second one is a decentralized Control problem (i.e. an infinite horizon linear-quadratic differential game). Then, while examining the optimal solution of each of the above strategies on the performance of the other, the necessary and sufficient conditions for the equivalence of the two problems are presented. In the absence of the conditions, by using the least-squares error criterion, an approximated CIHLQR Controller is presented. It is shown that the theorems could be extended from a two-agent Control system to a multi-agent system. Finally, the results are evaluated using the simulation results of a Two-Area non-reheat power system.

The fault tolerant Controller ((FTC)) issue is one of the most important subjects in the system theory and Control engineering which has many practical and industrial applications. In This paper, a new (FTC) has been designed in order to detect and compensate the sensors faults of permanent magnet synchronous motor (PMSM). To achieve this goal, sliding mode Controller (SMC) and PMSM vector Control have been used. In the faulty conditions, in order to achieve Control purposes, two sliding mode observers (SMO) estimate the speed and currents of motor. The observers create virtual sensors for the feedback Control. If sensors face with a condition that cause any fault, the (FTC) detects the fault and the virtual sensors are immediately used for sensorless Control of motor. The stability of the closed-loop system has been investigated by the Lyapunov stability theory. Simulation results confirm good performance of the proposed (FTC) for PMSM.